Contrary to previous studies, new research finds that the outcome of fertility treatment using sperm donors may not be dependent on a man's age, but the quality of their sperm.
Study co-author Dr. Navdeep Ghuman, of the Newcastle Fertility Centre at Life in the UK, recently presented the research at the European Society of Human Reproduction and Embryology (ESHRE) Annual Meeting in Munich, Germany.
The team says their findings may have important implications for current recommendations regarding the maximum age of sperm donors.
In the UK, current professional guidelines state that sperm should not be taken from donors aged 41 years or over, although this can be judged on a case by case basis. In the US, most sperm banks require donors to be between the ages of 18-39, while some even set the maximum age limit at 34.
According to the researchers, such guidelines are a result of past research that has suggested older men have lower sperm quality and are more likely to have DNA mutations that present an increased risk of genetic abnormalities in offspring.
Furthermore, studies have indicated that older men have lower semen volume, motility and concentration. But the researchers say this does not necessarily prevent conception.
Overall, the team says the association between age and sperm quality is under-researched, so they set out to investigate whether a man's age affects live birth rate from fertility treatment.
Analysis of all UK fertility treatment cycles between 1991 and 2012
The team, led by Dr. Meenakshi Choudhary of the Newcastle Fertility Centre at Life, analyzed all fertility treatment cycles with sperm donation in the UK between 1991 and 2012 using data from the Human Fertilisation & Embryology Authority.
Researchers say their findings suggest the outcomes of fertility treatment involving sperm donation are dependent on sperm quality rather than the age of the donors.
Of 230,000 sperm donation cycles during this period, the researchers included 39,282 that were first cycles by either in vitro fertilization (IVF) or donor insemination.
The researchers note that since female fertility is well known to decline with age, they divided the female study participants into two age groups: those who were treated with donor sperm between the ages of 18-34 and those who were treated after the age of 37. The two groups were then divided again dependent on whether their treatment was through IVF or donor insemination.
The team then divided the sperm donors into one of six age groups: under 20, 21-25, 26-30, 31-35, 36-40 and 41-45.
The researchers say that unsurprisingly, women who were treated with donor sperm after the age of 37 had a lower birth rate (14%) that those were treated between the ages of 18-34 (29%).
But they found that the age of a sperm donor did not appear to affect live birth rates among women who received donor sperm in the younger age group.
Of the women who received IVF between the ages of 18-34, sperm donors aged under 20 and 30 represented a live birth rate of 38.3%, while donors aged 41-45 represented a live birth rate of 30.4%. Of younger women who were treated with donor insemination, sperm donors under 20 represented a 9.7% live birth rate, while a 12% live birth rate was accounted for by donors aged 41-45.
However, the researchers noticed a different trend among women who underwent sperm treatment over the age of 37.
'Up to the age of 45, there is little effect of male age on fertility treatment outcome'
Among older women, younger sperm donors appeared less likely to produce a successful outcome than older donors.
They found that among older women who underwent IVF, sperm donors under the age of 20 represented an 11% live birth rate, those aged 26-30 represented a 17% live birth rate, and a 16.6% live birth rate was accounted for by donors aged 41-45. Of older women who underwent donor insemination, sperm donors under 20 represented a 3.1% live birth rate, while those aged 41-45 represented a 4.6% live birth rate.
But Dr. Choudhary notes that women in the older group were less likely to conceive than those in the younger group, who are described as being in the "peak of reproductive potential," therefore the link between older sperm donors and increased live birth rate is not statistically significant.
Explaining a potential reason behind this finding, Dr. Choudhary says:
"This trend of less likelihood of live birth with younger sperm donor age might simply be explained by the fact that younger men who donate sperm are less likely to have proven fertility themselves than older sperm donors with proven fertility."
Dr. Choudery believes that overall, their findings indicate that it is sperm quality, not the age of the donor that influences successful outcomes of fertility treatment. She says:
"Our results suggest that, up to the age of 45, there is little effect of male age on treatment outcome, but sperm donors are a selected population based on good sperm quality.
Our study shows that we are good at selecting the right sperm donors with the right sperm quality - and that's why we found no difference in live birth rate despite the increasing age of sperm donors. This confirms the view that a man's age doesn't matter in achieving a live birth provided his sperm quality is good."
In a recent spotlight feature, Medical News Today looked at whether infertility is primary seen as a woman's problem, and discussed whether there should be more focus on support and treatment for men with fertility problems.